How do you bypass an RV holding tank?

Presumably, you’re looking to convert your RV into a full-time stationary home. That would be about the only reason to bypass the holding tanks and if you did, just know that you’re probably greatly lowering any sort of resale value (unless it’s to resell the now stationary home).

One reason to bypass the holding tanks is the convenience of not having to dump and flush tanks.

If you do want to bypass the black water holding tank, you will need to change the RV toilet to a residential unit and most probably remove the holding tank. This is because the toilets that come with RVs do not flush the same way a residential toilet flushes.

If you try to use the RV-style toilet, you will have to live with the smell of sewer gasses coming out of the toilet every time you flush. RV toilets do not have a p-trap or a siphon pipe that blocks sewer gasses, nor do they actually flush the waste. When you open the flap valve of an RV toilet, the waste evacuates from the bowl by gravity, not the siphoning action present in residential toilets.

You would likely replace the RV’s plumbing with 3 inch PVC piping. You could still do this — from the RV’s original sewer pipe to the waste collection pipe in the ground — if you kept the RV-type toilet intact.

Remember that if you do retain the holding tank system, keep the valves closed until you dump and flush. Not keeping them closed will lead to waste solids accumulating in the holding tank.

If you definitely plan to make this a permanent home then you might want to consider a park model or single wide trailer instead. These units will not need any modifications to the sewer system and might be just as cost-effective once you factor in the cost of making modifications. A park model or single wide may also provide move livability – bigger space, appliances, water heater, and so on.